Monday, August 20, 2012

Immediately, I notice that the fan is not working. Although the Arduino can produce up to 5V, it can only produce up to 41 mA of current. The fan requires at least .07 Amps to operate. I will have to figure something out, or I'm left with a twitchy fan.

The gas sensors seem to work fine, though as before, they run quite hot. The Geiger Counter also works as expected, though it seems to pick up more radiation than before. I'm not sure what's causing this - perhaps there's something in another sensor that sets it off.

Other sensors don't seem to work at all. I finally figured out that it was because I soldered the connections wrong. Although the solderable breadboards I got are supposed to be like the regular bread boards, these seem to have an extra horizontal line of connected holes, unlike the bread boards I was working with. This threw me off as I was soldering, and, needless to say, I made a few mistakes.

Unfortunately, it takes a long time to re-solder everything since there's so many wires in the way, but I will finish my tomorrow and continue testing tomorrow.

Thursday, August 16, 2012

Here's the removable base with the Arduino and Geiger Counter circuit board attached. I have removed the actual tube since it will be placed on top of the box. The two black wires that I've soldered are going to connect to the tube.

The two green one connect to 5V and GND, and the blue wire is the data wire.

Note that you can also see the Velcro on the bottom of the base.

The Box:
The fan is in the back. The cutout is for the Arduino's ports. Note that there is also Velcro on the bottom of the box.

There are two little flanges that act as convenient handles for the box when you want to pick it up and move. The top will also be fastened on these flanges.

Oops! The fan cutout was slightly smaller than the actual fan. But it still looks nice don't you think?

Top:
The most complicated part of the box, featuring all of the sensors and their associated circuitry. I've only managed to finish the gas sensors and attach the Geiger Counter tube, the temperature/barometric pressure sensor, and the temperature/humidity sensor.

Everything together:

It's a wireforest! In a box! No but seriously, once I figure out where everything is placed, i will trim the wires a bit shorter and use some fasteners to make things more organized.

Tuesday, August 14, 2012

I decided to change one of the connectors to improve the design. The old connector only had one hole on the bottom, which meant that once you took off the top of the box, it could move or wobble. The new connector has two holes on the downwards facing side. This way, the connector won't move or wobble as much when you unscrew the top screw and take off the top of the box.

This meant that I would have to re-machine the walls as well, which I did:

(I messed up with one of the holes, which is why the wall piece on the right has three holes on top. But the extraneous hole will be covered by the connector anyways, so the aesthetics won't be compromised. =])

I also finished making the back wall. The rectangular cutout is for the ports on the Arduino.

Finally, I cut out some of the L-shaped connectors:

Tomorrow I will drill holes into them. This is the last part of my project that I have to machine, so after that, all that remains is the assembly (the fun part!).

Friday, August 10, 2012

Gas Sensor Base: This was all done by the laser cutter. The second try went much better than the first because I worked with a bigger piece of Plexiglas that allowed the machine more leeway to zero imprecisely.

After fininshing the base, I have to transfer the connections from my breadboard to my solderable breadboard that I machined a few days earlier. The solderable board has the same wiring as my breadboard, so it is easy to transfer connections.

After soldering everything together, I have to fix the gas sensors to the base I just machined. The gas sensors go into these little 7-pin vacuum tube sockets, which then sits snugly in the little holes on the base. I then solder the wires of the gas sensors onto the solderable breadboard and screw in some standoffs to create a small unit:

This will be later attached to the top of the box, on which we will install all of the other sensors. The four free wires are the data wires that will be connected to the Arduino.

Wednesday, August 1, 2012

It's been a while since I've posted, but that is because I've been busy working on the draft of the project box. Also because I love to render things.

I originally started with a long design that looks something like this:

The Arduino, green perf boards (roughly modeled), and the Geiger Counter breakout board would be laid on top of each other, with the fan on one end :

However, this was a bit unappealing as I realized that I had no good way of easily accessing the Arduino when trying to make changes. The box is about 3"x3"x6", and working within a 3" wide box seemed rather hard. Also, finding a good way of attaching the Arduino to the wall was difficult. The Arduino is wider than the Geiger Counter board, but just barely, making it actually impossible to use standoffs when both boards are stacked lengthwise. Thus, I scrapped this design.

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The new design features a more square box with dimensions of approximately 5" x 5.5" x 3.5". (The design also looks more sound simply because I've managed to render the standoffs.):

If you look closely, you'll notice that inside the box, both boards are placed inside a base. The base will be Velcro-ed to the bottom of the box, which allows you to make changes to the circuitry without having to take apart the whole box.

The box top is another assembly of many things. (Hopefully it should hold its weight.)

All the sensors are put on top of the box (as some sensors, especially the gas sensors, need to be in direct contact with the surroundings).Below the lid, there are two perf boards that house all the other electronics such as your capacitors and resistors. The gas sensors are also placed on an elevated platform so that air blown out from the fan will be able to create some kind of airflow around the sensors. This elevated platform is also removable:

I have rendered it so that there is space for 7 sensors (hopefully - the actual sensor sockets haven't arrived yet so I'm still unsure about those dimensions), but it seems that I am only able to work with 4 sensors now as the order of additional sensors haven't yet arrived. Put together, everything looks like this:

You'll notice that the top sticks out a bit at the edges. I plan fix the lid in place by using L-shaped aluminum bars with screws and nuts attached on the underside of the lid and walls. This makes it easier to remove the lid when you need to make changes. Since I have not yet rendered any kind of fasteners, I drew a rough sketch of what I meant:

When you want to remove the lid, you only have to unscrew the screw (circled in red) that goes through the lid. And when you want to reattach the lid, the screw is put back into place along with a nut (not shown) on the outside of the box, making it much easier to assemble.

Of course, before I make anything, I will first have to confirm the design with mentors (which I am doing today).